The Madeleine Brand Show for April 9, 2012

Biologist claims certain chemicals increase chance of obesity

Ilsa Setziol/KPCC

Molecular biologist Bruce Blumberg in his lab and UC Irvine

Ilsa Setziol/KPCC

Molecular biologist Bruce Blumberg examines cells in his lab at UC Irvine


Obesity is at epidemic proportions in this country.

But what if some people are overweight, not only because of the brownies they eat, but because of the plastic containers they store them in?

The conventional theory goes that people become obese because they take in more calories than they burn off. But molecular biologist Bruce Blumberg says it’s more complicated than that. 

"If it were a simple problem, a matter of balancing our caloric checkbook, no one would be fat," says Blumberg. "We are not a country full of lazy people who just eat everything in sight."

In his lab at UC Irvine, some of his mice are obese. Blumberg made them that way, but not by overfeeding them.
"My mice become fatter on a normal diet," Blumberg explains. "That’s only because they were exposed to this chemical in the womb."
 
The chemical he’s talking about is called Tributyltin. It’s used to preserve wood and is found in some vinyl products. There are more than a dozen kinds of drugs and chemicals that make lab animals — or people — fat. Blumberg calls them obesogens.

He says fat cells start out as a kind of stem cell with the potential to become a variety of cells, including bone and muscle. But Tributyltin alters that process "and it tells the population of cells that no matter what stimulus you receive you are going to make a disproportionately high number of fat cells," according to Blumberg.
 
Blumberg can’t say how many Americans have tributaltin in their bodies; no large scale studies have been done. But other suspected obesogens are commonly found in people, including one chemical used in plastics and another found in nonstick cookware and microwavable food containers.

There may be more than one way obesogens affect metabolism. "The way we’re thinking of it is the perfect storm for obesity," says Jerry Heindel, a program administrator for the National Institute of Environmental Health Sciences.
 
Heindel has examined obesogens for the National Institutes of Health.

"They cause more fat cells or alter your desire for food," he explains. "These are programmed into you for the rest of your life."
 
But do these chemicals really harm people — or just lab animals? Toxicologist George Gray of George Washington University says that it’s too soon to say.
 
"We just don’t have as much information as we’d like," he admits.
 
Gray says animal studies can be good predictors of health effects in humans, except for when they're not.
 
"We don’t know if this obesogen research is one where mice tell us what’s happening or if it’s one where we have to be a little more careful," he says.
 
Obesogen research is part of the emerging field of endocrine disruption, the study of how tiny amounts of chemicals can mimic hormones or otherwise trip up the endocrine system.
 
So far, there is no federal regulation of most endocrine disruptors. But Gray says the EPA has been evaluating them for more than a decade.

"They have found it a real challenge," he says, "to develop tests for these very low dose effects."
  
Bruce Blumberg disagrees. 

"The industry has muddled up the issue," he maintains. "The EPA can’t come up with any good tests because the industry guys don’t buy in."
 
Long-term studies on obesogens in people are underway. Meantime, Jerry Heindel advises that consumers "watch the use of plastics" and "eat more fresh fruits and vegetables rather than canned things."
 
Still, Heindel says poor diet and lack of exercise likely contribute more to obesity than chemicals.


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